... Tonight's Sky . ... Observing . ... Sky this Month . ... Astronomy for Kids . ... Can you explain Mercury's retrograde motion? Do other planets appear to do this also? ... When astronomers talk about retrograde motion, generally they refer to the apparent motion outer planets make as Earth passes them while orbiting the Sun. ... Get instant access to subscriber content on Astronomy.com! ... Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter. ...

Astronotes Armagh Planetarium's Stellar Blog! ... Planets . ... Monthly Sky Notes . ... October . ... By admin October 8, 2010 Posted in: Monthly Sky Notes . A giant from close up: an image made using data from the Cassini probe which flew past Jupiter in 2000. ... As it is so far from us, it takes JupiterтАЩs light a significant time to reach us тАУso when you see Jupiter tonight you are seeing it as it was 35€а minutes in the past. ... Posted October 12, 2010 at 11:15 PM . ... Astronotes . ...

home publications > mercury . SEARCH ASP SITE: Match ALL words Match ANY word . ... Publications of the ASP (PASP) . ... A Minor Planet's Night Out . ... Orbiting between Mars and Jupiter are thousands of rocky bodies. ... In 1804 came Juno; in 1807, Vesta. ... Most minor planets, as asteroids are sometimes affectionately called, hum in elliptical orbits between Mars and Jupiter. ... This helps us as we select the Guest Observer, and it helps readers to understand what you studied. ...

The Discovery of the Galilean Satellites . ... Probably the most significent contribution that Galileo Galilei made to science was the discovery of the four satellites around Jupiter that are now named in his honor. Galileo first observed the moons of Jupiter on January 7, 1610 through a homemade telescope. He originally thought he saw three stars near Jupiter, strung out in a line through the planet. ... Galileo's Observations of Jupiter's Moons . ... Jupiter . ...

... Bad Astronomy . ... Mad Science . ... Site Info . ... Public Talks . ... Keep Bad Astronomy close to your heart, and help make me filthy rich. ... Who is this guy who calls himself "The Bad Astronomer?" ... First, yes, I am a real live astronomer (when people ask me what astronomers do, I tell them "They astronom !" ... These are emitted by powerful objects like black holes, exploding stars, and super-dense neutrons stars. ... Finally, am I really a bad astronomer? ... 2008 Phil Plait. ...

Aristarchus of Samos, around 200 BC, proposed that the Earth revolved around the Sun, but found few supporters. ... For a discussion of the discovery of the solar system which includes a "moving picture" illustrating retrograde motion, click here . ... The Sun and Moon, he claimed, obviously moved around Earth. ... The full story of the discovery of the solar system--of Copernicus, Galileo, Tycho and Kepler--is long and would take this discussion too far afield. ... Nicolaus Copernicus . ...

... A discussion of retrograde motion of planets helps the students understand the logic underlying the ideas of both Ptolemy and Copernicus. ... This lesson plan supplements: "The Discovery of the Solar System," section #9c: on disk Ssolsys.htm , on the web . ... Learn about the system proposed by Copernicus, and the way it explained retrograde motion: all planets moved in circles around the Sun, but the ones closer to the Sun always moved faster. ... Did this predict correct planetary motions? ...

... A wordlwide network of amateur and professional astronomers record and time the mutual eclipses and occultations of the Galilean satellites as accurately as possible. ... Already, the acceleration of Io is evident in the data and continued monitoring through this coming season will help pin down the acceleration of the other three satellites. ... From Dr Apostolos Christou, Armagh Observatory: . ... If you want to know the observing times from your location get it by filling in this form . ...

... 2010 October 8 . Two Planet Opposition . ... Explanation: In late September, two planets were opposite the Sun in Earth's sky, Jupiter and Uranus. ... The faint greenish disk of distant planet Uranus is near the upper left corner. Of the tilted planet's 5 larger moons , two can be spotted just above and left of the planet's disk. ... Farthest from Jupiter is Callisto , with Europa and Io all left of the planet's disk, while Ganymede stands alone at the right. ... About APOD | ...

... Neptune, the Solar System's outermost gas giant planet, is 30 times farther from the Sun t